A highly selective wavelength-ratiometric and colorimetric probe for cysteine

Based on the nucleophilic aromatic substitution reaction mechanism, a new highly selective probe for cysteine (Cys), N-butyl-4-bromo-3-nitro-1,8-naphthalimide (1), was designed and synthesized. The probe displayed a remarkable (58 nm) red-shift in the absorption spectra and the color changes from colorless to yellow upon reaction with Cys. The probe could detect Cys quantitatively in the range of 0–0.9 mM by both normal and ratiometric absorption spectrometry methods. Moreover, 1 could also serve as a “naked-eye” probe for Cys with a minimum detectable concentration of approximately 50 μM.

► We have reported a highly selective colorimetric cysteine probe. ► The probe was based on the nucleophilic aromatic substitution reaction mechanism. ► It could be used for the ratiometric quantification of cysteine. ► It’s working range covering the physiological level of cysteine in normal organisms. ► It also could be used as a “naked-eye” probe for the detection of cysteine.